As bandwidth continues to grow, capacity is being stretched in fiber optic networks. Various advanced techniques are used to provide additional bandwidth including advanced coherent modulation techniques, polarization multiplexing, flexible grid spacing, and the like. With these advanced techniques, fiber optic systems suffer new degrees of susceptibility to transients on a time varying optical channel, including polarization transients, etc. As described herein, an SOP transient source causes an SOP transient which is anything that causes quick changes in the SOP of signals on an optical fiber. Coherent fiber optic systems are configured to track SOP changes as part of normal operation, but when quick SOP transients occur, these can be outside the tracking ability of fiber optic systems, leading to errors, loss of framing, etc. Example SOP transient sources can include, without limitation, external vibrations (e.g., bridges, roads, railroads, wind, etc.), bad splices on the optical fiber, weather (e.g., lighting, wind, etc.), or the like. Usually, SOP transient sources behave unpredictably and from unknown locations in the fiber. Further, SOP transient sources can be Time of Day specific, seasonal, etc. SOP transients can be particularly problematic with coherent transmission, and especially difficult to localize/isolate given their nature in general. That said, it would be advantageous to localize SOP transient sources so that proactive/preventative maintenance can occur.
Existing techniques to localize/isolate SOP transients can include a span-by-span determination based on faults or bit error rates in a coherent signal. However, these techniques only provide isolation to a specific span, which could be a few kilometers to over 100 km, and require actual faults or errors to identify. This is not enough resolution to perform preventative maintenance to root out the SOP transient source.